Background. We sought to determine and compare the prevalence of the Metabolic Syndrome (MS) in patients with acute myocardial infarction (AMI) utilizing the new International Diabetes Federation (IDF) definition with the older National Cholesterol Education Program (NCEP) definition. We also examined the clinical utility of MS in this context. Methods. A total of 107 consecutive patients with AMI were prospectively evaluated for MS. Fasting lipids obtained at admission and fasting glucose at discharge were used. A postdischarge folder audit verified rates of discharge coding and implementation of specific management strategies for MS. Results. Baseline patient characteristics included: mean age 59 +/- 13 years; males 80 ; diabetes 19 ; mean BMI 29.7 +/- 8.4 kg/m(2). MS prevalence was 54 by the IDF definition and 49 by the NCEP definition, with good agreement between definitions: kappa = 0.664, P <.001. Factors predictive of MS after multivariate analysis included: hypertension, fasting glucose, waist circumference, and serum HDL (all P <.05). Despite the high prevalence, MS was recognized at discharge in only 1 patient, and referral for exercise and/or weight-loss programs was undertaken in 5 patients. Conclusion. There is a high prevalence of MS utilizing contemporary definitions in patients with AMI: 54 by the IDF definition and 49 by NCEP criteria. Despite the high prevalence, MS was under-recognized and under-treated in this population.